I just noticed that my chicken is bleeding around the tail area and missing a large patch of feathers. I looked this problem up and some said that the other chickens are picking on her but it might also be a parasite or bug. She is only 12 weeks old so I thought that the feathers might have just taken a little while to grow in but now that I see blood I am very worried. She might be picking at the feathers because I saw another one doing that as well but not to the point of blood. How should I clean the patch of blood? Could you help me figure out the cause of this problem? How can I prevent this from happening again?